Cabinets for rack mounted components must accommodate the need for both air flow and noise attenuation with respect to the cumulative requirements of diverse components that may be selected for mounting within the enclosure. Higher, more concentrated heat loads often increase not only the need for increased cooling air flow, but also the level of noise that must be attenuated. Further, neither the selection of rack mounted components, the positioning of such components within the enclosure, nor the overall cooling or noise attenuation requirements are subject to control by the designer of the equipment enclosure.
Heat loads in rack mounted computer equipment continue to rise with corresponding higher cooling requirements. In order to provide air cooling solutions, an increase in the volumetric air flow is required. The higher volumetric air flow is normally accompanied by higher acoustic noise levels which can result in a total system noise level that the customer will not accept or tolerate. One solution is to use doors with high acoustical noise attenuation. However, doors with high noise attenuation capability are prone to possess high air flow impedance and uneven air flow distribution as structures are employed to limit acoustical line of sight and physical depth is limited to minimize system footprint.
High air flow impedance can not be tolerated, since the enclosure system must be compatible with the cooling needs of the rack mounted components and not diminish the capability of the individual components to provide adequate cooling. If the impedance of the acoustical door is too high, it can also increase the flow balancing problems between rack modules with different types and sizes of air moving devices. Racks can house many different types of rack modules with different inlet and outlet air flow locations making necessary the uniform distribution of the incoming air at the rear of the door important for adequate rack module cooling. This design constraint is not made easier by the attempt to minimize the distance between the enclosure door and the rack mounted components in the attempt to minimize the overall depth of the enclosure. Minimizing the depth of the door also increases the difficulty of providing low impedance and high acoustic attenuation.
In addition to the acoustic and air flow design considerations, the enclosure door must be capable of opening to a position allowing full frontal access to the rack mounted component area when such electrical equipment enclosures are located with like enclosures at each side with side walls abutting.